Influence of ionic speciation on electrocatalytic performance of polyaniline coated platinum electrode: Fe(III)/Fe(II) redox reaction (original) (raw)
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Catalytic polyaniline-supported electrodes for application in electrocatalysis
Journal of Solid State Electrochemistry, 2003
Polyaniline (Pani) films prepared on Au wires were employed as substrates to deposit Pt, Pt-Ru, Pt-Os, Pt-Mo and Pt-Ru-Os or Pt-Ru-Mo by using appropriate working solutions and a potential-programmed perturbation. The atomic percentages of the different metals on Pani were determined by EDAX and their particle size and distribution by SEM. The catalytic activity was tested for adsorbed CO and CH 3 OH electrooxidation. Accordingly, the best binary and ternary metal combination resulted in Pt-Ru and Pt-Ru-Os.
Mediated Electrocatalysis at the Electrodes Covered with MIII(bpy)33 (M=Co and Fe) in the Presence of Electroactive Solutes
Electroanalysis, 2003
Electron transfer processes for selected redox systems (ferrocene0/+, decamethylferrocene0/+, N,N,N′,N′-tetramethyl-1,4-phenylenediamine0/+, 7,7,8,8-tetracyano-quinonedimethane0/−/2−, cobaltocene0/+, C600/−, and benzoquinone0/−) at electrodes modified by precipitation of electrochemically inactive [MIII(bpy)3](ClO4)3 (M=Co and Fe, bpy=2,2′-bipyridine) layers have been investigated by cyclic voltammetry and electrochemical quartz crystal microbalance studies. The mediation of heterogeneous electron transfer is observed for these systems. For an electrode modified with [MIII(bpy)3](ClO4)3, the rate of the electrocatalytic mediation process depends on the formal potential of the redox system. If the formal potential of the redox system is close to the potential of [CoII(bpy)3]2+ oxidation (as is the case with the decamethylferrocene0/+, N,N,N′,N′-tetramethyl-1,4-phenylenediamine0/+ and 7,7,8,8-tetracyanoquinonedimethane0/− systems), the rate of the electrode reaction is limited by the rate of the chemical reduction of the [CoIII(bpy)3](ClO4)3 solid phase by the reduced form of redox couple. For C60 and benzoquinone, which have more negative formal potentials for reduction, the rate of diffusion of the electroactive reactant to the electrode surface limits the rate of electrode process. The kinetics of mediated electrocatalysis are also affected by the solvent. In the case of the Fe(III)-based layer, the diffusion of the electroactive reactant in the solution is the rate determining step for the catalytic process at the modified electrode for all studied systems. Electrodes modified with [FeIII(bpy)3](ClO4)3 have been used for the quantitative determination of electroactive compounds. For ferrocene and decamethylferrocene, a linear relationship between the catalytic reduction current and the concentration of reactant in the solution has been observed over the concentration range from 1 to 50 mM.
Materials Chemistry and Physics, 2021
Abstract Polyaniline-Silica (PANI-SiO2) nanocomposite was developed as a support for enhancing the performance of Pt/Ni electrocatalyst in direct methanol fuel cells (DMFCs). Bimetallic Pt/Ni electrocatalyst was deposited on the in-situ prepared PANI-SiO2 nanocomposite via cyclic voltammetry (CV) method. The electro-oxidation of methanol was studied at room temperature using CV, linear sweep voltammetry (LSV), and chronoamperometry (ChA) tests. The Pt/Ni/SiO2-PANI electrocatalyst resulted in an onset potential of −0.54 V and an excellent peak current density of 144 mA/cm2 showing its outstanding catalytic activity. Moreover, the Pt/Ni/SiO2-PANI electronic structure was theoretically investigated via density functional theory (DFT) calculations. The DFT results confirmed that employing the PANI-SiO2 structure for bimetallic PtNi nanostructure could lead to increasing the reactivity of the resulting catalyst and decreasing the energy gap. This observation was well consistent with the experimental results. The experimental and theoretical data indicated that PANI-SiO2, as an organic-inorganic hybrid catalyst support, considerably improved the stability and CO poisoning tolerance of the resulting electrocatalyst, both of which are crucial for practical alkaline direct methanol fuel cell applications.
Materials Chemistry and Physics, 1996
Polypyrrole (Au/PPy) and polyaniline (Au/PAni) electrodes were prepared and their activities towards oxygen reduction in acid medium were examined. The insertion of iron or cobalt phthalocyanines into the conducting polymer during the electropolymerisation process was carried out and the modified electrodes were characterised by esr and uo-visible differential reflectance spectroscopies. The electrocatalytic behaviour of such electrodes towards oxygen reduction was examined. The influence of the central metal of the macrocycle and of the kind of polymer was investigated. It appears that the modified electrodes containing iron tetrasulfonated phthalocyanine are the most active ones but they are less stable than electrodes containing cobalt tetrasulfonated phthalocyanine. The comparison of the electrocatalytic behaviour of the Au/polymer-FeTsPc electrode with that of a bare platinum electrode towards oxygen reduction indicates that the reduction process is the same for both electrodes. The Au/polymer-FeTsPc electrode allows then to reduce the oxygen molecule mainly &I the 4-electron process into water as main product. In the case of the Au/polymer-CoTsPc electrode, the role of the conducting polymer in the whole reduction process is demonstrated. The Au/PAni-CoTsPc electrode allows to reduce the oxygen molecule mainly cia the 2-electron reaction into hydrogen peroxide, whereas the Au/PPyCoTsPc electrode allows it to reduce into water via the hydrogen peroxide formation for potentials lower than 0.4V rhe.
Speciation of iron(II) and iron(III) using a dual electrode modified with electrocatalytic polymers
Analytical Chemistry, 1992
Speciation of metal ions has received considerable attention in diverse areas such as ecotoxicology,' geology,2 process analysis,3 and aquatic studies: Several approaches have been adopted for the speciation of Fe(I1) and Fe(II1). Electrochemical methods predominate in this type of but chromatographid' and spedrometrii?~' methods have also been described. For the chromatographic and the spectrometric methods, interconversion from one redox state to another? the use of different chelating agents? or the use of more than one detection system6 is required to differentiate between the two redox states. Polarographic methods appear almost universal in the electrochemical approach, but as the Fe-(II)/Fe(III) couple is reversible,'O the use of reagents to separate the half-wave potentials (Ell2) for the oxidation and reduction processes is necessary. Several reports concerning the determination of Fe(II) and Fe(III) at solid electrodes have also appeared."J2 However, the redox chemistry of the Fe-(II)/Fe(III) couple is poor at glassy carbon,ll and at platinum, electrode fouling is encountered.12
A new grafted polymer electrode (GPE) (polystyrene as polymer) was grafted with acrylonitrile as a monomer using gamma irradiation to produce a new grafted polymer. The redox process of K 3 Fe(CN) 6 during cyclic voltammetry was studied by the new GPE. The ratio of Ipc/Ipa [1 of GPE to GCE Ipc/Ipa = 1.7, indicating that this electrode is a reversible electrode and can be used in conductivity studies by voltammetric analysis. The physical properties of the new electrode GP have good hardness, insolubility, and stability at different high temperatures and at different pH. Also, the sensitivity under conditions of cyclic voltammetry is significantly dependent on pH, electrolyte, and scan rate. At different scan rates, two oxidation peaks and two reduction peaks of Fe(III) were observed in a reversible process: Fe(III) Fe(II), and Fe(II) Fe(0). Interestingly, the redox reaction of Fe(III) solution using GPE remained constant even after 15 cycles. It is therefore evident that the GPE possesses some degree of stability. The potential use of the grafted polymer as a useful electrode material is therefore clearly evident.
Grafted polymer electrode (GPE) (polystyrene grafted with acrylonitrile as a monomer using gamma irradiation) was successfully fabricated as a working electrode using at cyclic voltammetry. The redox process of ferrocene in a non-aqueous electrolyte during cyclic voltammetry was studied. It was found that the redox current peaks of ferrocene ion Fe(II)/Fe(III) in non-aqueous electrolyte is very high oxidative current of 600µA at GPE, while at glassy carbon electrode (GCE) it is 80 µA. Also, the reduction current is high value (200 µA) at grafted polymer electrode and low value (50 µA) at GCE; indicating a good conductivity of GPE and hence, can be used for voltammetric analysis. The physical properties of GPE include good hardness, insoluble in non-aqueous electrolytes (except dimethyl formamide and chloroform) and good stability at different solvents. Besides, the sensitivity under conditions of cyclic voltammetry is significantly dependent on the scan rate and variation in concentration. At different scan rates, redox peaks of ferrocene were observed in a reversible process: Fe(II)/Fe(III).
Electrochemical promotion of Pd, Fe and distributed Pt catalyst-electrodes
Solid State Ionics, 2000
This paper describes recent results of the use of the effect of non-faradaic electrochemical modification of catalytic activity (NEMCA) or Electrochemical Promotion (EP) in the following systems, which are of potential practical interest: (i) C H 2 4 oxidation on electronically isolated Pt catalysts on YSZ, where NEMCA is induced via potential application between two terminal Au electrodes also supported on the solid electrolyte (wireless configuration), (ii) NH decomposition on Fe catalyst 3 electrodes interfaced with CaZr In O , a proton conducting solid electrolyte support using a single pellet configuration 0.9 0.1 32a 1 and (iii) Selective C H hydrogenation on Pd catalyst electrodes interfaced with b0-Al O , a Na conductor, using a 2 2 2 3
A grafted polymer reference electrode (GPRE) (polystyrene grafted with acrylonitrile as a monomer using gamma irradiation) was fabricated as a reference electrode using cyclic voltammetry (CV). The redox process of K 3 Fe(CN) 6 during CV was studied. It was found that the redox current peaks of Fe(II)/Fe(III) in 0.1 M of KCl as supporting electrolyte is given the same oxidation-reduction current as in the Ag/AgCl reference electrode, indicating a good result of GPRE and, hence, it can be used for voltammetric analysis technique. The physical properties of GPRE include good hardness, insoluble in non-aqueous electrolytes (except dimethyl formamide and chloroform), and good stability at different solvents. In addition, the sensitivity under conditions of CV is significantly dependent on the scan rate (SR) and variation in concentration. At different SRs, redox peaks of K 3 Fe(CN) 6 were observed in a reversible process: Fe(II)/Fe(III). Interestingly, the redox reaction of Fe(II)/Fe(III) solution using GCE versus GPRE remains constant even after 15 cyclings. It is therefore evident that the GPRE possesses some degree of stability. Also, the new reference electrode GPRE has improved the properties of electroanalysis of CV on the working electrode GCE in reliability with the relative standard deviation.